| High temperature block copolymers and process for making same -> Monitor Keywords |
|
|
 
High temperature block copolymers and process for making sameHigh temperature block copolymers and process for making same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080039584, High temperature block copolymers and process for making same. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001]This invention relates to novel polymerization processes to prepare alpha-methyl-styrene (aMS)/styrene (S) copolymers and block copolymers comprising the save in which high conversions of aMS are achieved. The invention also relates to elastomeric block copolymers comprising aMS/S blocks having high glass transition temperatures. The invention further relates to compounds comprising the elastomeric block copolymers which demonstrate excellent high temperature performance. BACKGROUND OF THE INVENTION [0002]Alpha-methyl-styrene (aMS) is a technologically interesting monomer for homo- or copolymerization because of the resulting high glass transition temperature (Tg) of the polymers incorporating it. Inclusion of aMS as a comonomer with monovinyl-aromatic monomers such as styrene allows tailoring of the Tg of styrenic blocks. This is particularly suitable in anionic polymerizations where both aMS and styrene readily polymerize. Further, such high temperature glassy blocks can be expected to increase the service temperatures of thermoplastic block copolymers into which they are incorporated. [0003]One well known problem associated with aMS polymers is their low ceiling temperature (Tc). The ceiling temperature is the temperature above which a polymer can spontaneously depolymerize. This presents a problem during polymerization where temperatures must be carefully maintained below Tc. Further, in elevated temperature applications aMS homopolymers will thermally decompose readily above Tc once decomposition is initiated by any process. One approach used to mitigate this problem is to copolymerize aMS with comonomers having high Tc. Such is the case with copolymers of aMS and styrene. [0004]As second problem, heretofore unsolved, is the polymerization of aMS polymers, particularly copolymers with monovinyl-aromatic monomers, in which high conversions of aMS are achieve. This is important for the practical reason of avoiding difficult and expensive recycle operations. Also, in block copolymerization efficient consumption of the aMS monomer can prevent contamination of non-glassy blocks with the high Tg aMS. [0005]Block copolymers have previously been prepared comprising aMS/S endblocks as taught in GB Patent 1,264,741. The polymerization was conducted to synthesize blocks having randomly distributed comonomers. The glassy endblocks of these block copolymers comprised a majority of aMS and between 10 and 40 mol % of styrene monomer. Importantly, the process required to synthesize these block copolymers was conducted at cold or cryogenic temperatures from -10 to -100.degree. C. [0006]Tapered block copolymers containing aMS have been taught in U.S. Pat. No. 4,427,837. The process taught therein suffered from conversions of less than 10% of the aMS monomer. Thus, large excesses of aMS monomer were required to incorporate modest amounts in the final polymer. Recovery of the unpolymerzied aMS monomer presents a significant practical problem. [0007]Fully hydrogenated styrene/aMS/diene block copolymers have been taught in US Patent Application 2003/0065099. Small amounts of polar co-solvent were utilized in order to facilitate cross-over from the butadiene to the styrene/aMS. However, this process also suffered from very low conversions of the aMS monomer. [0008]There yet exists a need for a process to copolymerize aMS/monovinyl-aromatic monomers which can be conducted at practical polymerization temperatures and which achieves high conversion of the aMS monomer. Such a process will allow the construction of block copolymers having high Tg glassy blocks and such block copolymers will be useful in making high service temperature rubber compounds. The present invention is directed to such a process, high Tg block copolymers and rubber compounds made from them. SUMMARY OF THE INVENTION [0009]In one embodiment the invention is a process for the preparation of block copolymers, and block copolymers made by the process, comprising adding alpha-methyl-styrene to an inert solvent wherein at the end of the subsequent copolymerization step, the solids content is from 20 to 50 wt % such that the concentration of living polymer-Li chain ends is from 500 to 2500 ppm and wherein the amount of alpha-methyl-styrene is from 25 to 50 mol % on the basis of the total amount of styrene and alpha-methyl-styrene, adding a polymerization modifier, adding an anionic polymerization initiator, adding styrene monomer continuously and copolymerizing said styrene and alpha-methyl-styrene to form a living glassy block at a temperature from 35 to 60.degree. C. wherein said copolymerization is conducted in such a manner as to maintain a high concentration of alpha-methyl-styrene relative to styrene for the majority of the copolymerization achieving at least 45% conversion of the alpha-methyl-styrene, adding a conjugated diene of a mixture of conjugated dienes, and polymerizing said conjugated diene or mixture of conjugated dienes to form a living elastomeric block wherein the conversion of the conjugated diene or mixture of conjugated dienes is at least 90%. [0010]In a another embodiment the invention is an elastomeric composition comprising a block copolymer having at least one glassy block consisting of a mixture of styrene and alpha-methyl-styrene wherein the amount of alpha-methyl-styrene in the glassy block and the peak molecular weight of the glass block is from 2,000 to 3,000 g/mol, and at least one elastomeric block comprising a conjugated diene or a mixture of conjugated dienes wherein the elastomeric block has a molecular weight from 20,000 to 300,000 g/mol and the amount of the glassy block is from 10 to 40 wt % and an olefin polymer or copolymer. [0011]In a further embodiment the invention is a selectively hydrogenated elastomeric block copolymer comprising at least one glassy block and at least one elastomeric block wherein the glassy block is a copolymer of an alpha-alkyl-vinyl-aromatic and monovinyl-aromatic monomers and where the molar ratio of alpha-alkyl-vinyl-aromatic monomer to monovinyl-aromatic monomer is from 25/75 to 50/50, the elastomeric block is a block of at least one polymerized conjugated diene having a vinyl content from between 20 to 85%, subsequent to hydrogenation from 0 to about 10% of the arene double bonds in the glassy block have been reduced and at least 90% of the conjugated double bonds have been reduced, each glassy block has a peak molecular weight from 2,000 to 30,000 g/mol and each elastomeric block has a peak molecular weight from 20,000 to 300,000 g/mol, the amount of glassy block is from 10 to 40 wt % on the basis of the total block copolymer mass, and the glass transition temperature of the glassy block is from 120 to 140.degree. C. BRIEF DESCRIPTION OF THE DRAWINGS [0012]FIG. 1 is a GPC chromatogram of inventive polymer 5 from Example II. DETAILED DESCRIPTION OF THE INVENTION [0013]The process of the present invention is a unique polymerization process developed for the anionic synthesis of alpha-alkyl-vinyl-aromatic and monovinyl-aromatic copolymers and block copolymers containing them. The general features of anionic polymerization, for example solvents, initiators, and coupling agents, may be applied to the current invention. The unique aspects of the process involve comonomer addition schemes, solids content ranges, preferred copolymerization temperatures and polar co-solvents among other features described herein. [0014]In particular, the inventive process is utilized to synthesize thermoplastic block copolymers having high glass transition temperature (Tg) glassy blocks. As used herein "thermoplastic block copolymer" is defined as a block copolymer having at least one glassy block generally polymerized from alpha-alkyl-vinyl-aromatic and monovinyl-aromatic monomers and at least one rubbery block generally polymerized from one or more dienes. The present invention includes as an embodiment a thermoplastic block copolymer composition, which may be a diblock, triblock copolymer, or multi-block composition. In the case of the diblock copolymer composition, one block is the glassy alpha-alkyl-vinyl-aromatic/monovinyl-aromatic copolymer block and the second polymer block is elastomeric and is substantially composed of conjugated diene. In the case of the triblock composition, it comprises glassy endblocks and an elastomeric midblock. Where a triblock copolymer composition is prepared, the conjugated diene block can be designated as "B" and the alpha-alkyl-vinyl-aromatic/monovinyl-aromatic blocks designated as "A" and "C". The A-B-C, triblock compositions can be made by sequential polymerization. A-B-A triblock compositions can be made by coupling living A-B diblocks. In addition to the linear triblock configurations, the blocks can be structured to form a radial (branched) polymer, (A-B).sub.nX, or both types of structures can be combined in a mixture. Some A-B diblock polymer can be present. [0015]As defined, a high Tg value means having a glass transition temperature greater than 100.degree. C. Typically, styrenic polymers including styrenic block copolymers have a glassy block Tg value approaching 100.degree. C. One object of the present invention is to construct block copolymers having glassy blocks comprising alpha-alkyl-vinyl-aromatic/vinyl aromatic copolymer blocks having a glass transition temperature greater than that resulting in a monovinyl-aromatic homopolymer block. For instance, homopolymer styrene blocks of sufficiently high molecular weight have a Tg value near 100.degree. C. Copolymerization with an alpha-vinyl-aromatic monomer such as alpha-methyl-styrene can lead to increases as large as 40.degree. C. IN the present invention, the copolymer block comprising alpha-alkyl-vinyl-aromatic and monovinyl-aromatic monomers has a value from 120 to 140.degree. C. Preferred are copolymer blocks having Tg values from 130 to 140.degree. C. [0016]The monomers used in the amionic polymerization process of the present invention include monovinyl-aromatic monomers, alpha-alkyl-vinyl-aromatic monomers and conjugated dienes. The alpha-alkyl-vinyl-aromatic monomer can be selected from alpha-methyl-styrene (aMS), alpha-ethyl styrene and substituted alpha-alkyl styrenes such as paramethyl-alpha-methyl-styrene and the like. Of these, alpha-methyl-styrene (aMS) is the most preferred. The monovinyl-aromatic monomer can be selected from styrene, para-methylstyrene, vinyl toluene, vinylnaphthalene, and para-tert-butyl styrene or mixtures thereof. Of these, styrene is most preferred and is commercially available, and relatively inexpensive, from a variety of manufacturers. The conjugated dienes for use herein are 1,3-butadiene and substituted butadienes such as isoprene, piperylene, 2,3-dimethyl-1,3-butadiene, and 1-phenyl-1,3-butadiene, or mixtures thereof. Of these, 1,3-butadiene and isoprene are most preferred. As used herein, and in the claims, "butadiene" refers specifically to "1,3-butadiene". [0017]The solvent used as the polymerization vehicle may be any hydrocarbon that does not react with the living anionic chain end of the forming polymer, is easily handled in commercial polymerization units, and offers the appropriate solubility characteristics for the product polymer. For example, non-polar aliphatic hydrocarbons, which are generally lacing in ionizable hydrogen make particularly suitable solvents. Frequently used are cyclic alkanes, such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane, all of which are relatively non-polar. Other suitable solvents will be known to one skilled in the art and can be selected to perform effectively in a given set of process conditions, with temperature being one of the major factors taken into consideration. [0018]Anionic polymerization initiators in the present invention include, for example, alkyl lithium compounds and other organolithium compounds such as s-butyllithium, n-butyllithium, t-butyllithium, amyllithium and the like, including di-initiators such as the di-sec-butyl lithium adduct of m-diisopropenyl benzene. Other such di-initiators are disclosed in U.S. Pat. No. 6,492,469. Of the various polymerization initiators, s-butyllithium is preferred. The initiator can be used in the polymerization mixture (including monomers and solvent) in an amount calculated on the basis of one initiator molecule per desired polymer chain. The lithium initiator process is well known and is described in, for example, U.S. Pat. Nos. 4,039,593 and Re. 27,145, which descriptions are incorporated herein by reference. [0019]Another effect of the polymerization modifier in present invention is to control the microstructure of vinyl content of the conjugated diene in the elastomeric block. This is particularly important when the elastomeric blocks will be hydrogenated. The term "vinyl" refers to the presence of a pendant vinyl group on the polymer chain. When referring to the use of butadiene as the conjugated diene, it is preferred that about 20 to about 85 mol percent of the condensed butadiene units in the copolymer block have 1,2 vinyl configuration as determined by proton NMR analysis. For selectively hydrogenated block copolymers, preferably about 30 to about 70 mol percent of the conjugated diene units should have vinyl configuration. Continue reading about High temperature block copolymers and process for making same... Full patent description for High temperature block copolymers and process for making same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this High temperature block copolymers and process for making same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like High temperature block copolymers and process for making same or other areas of interest. ### Previous Patent Application: Adhesive composition Next Patent Application: Thermosetting resin composition, thermosetting film, cured product of those, and electronic component Industry Class: Synthetic resins or natural rubbers -- part of the class 520 series ### FreshPatents.com Support Thank you for viewing the High temperature block copolymers and process for making same patent info. IP-related news and info Results in 0.15077 seconds Other interesting Feshpatents.com categories: Medical: Surgery , Surgery(2) , Surgery(3) , Drug , Drug(2) , Prosthesis , Dentistry 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
